Method of producing zeolite encapsulated nanoparticles

ABSTRACT

The invention therefore relates to a method for producing zeolite, zeolite-like or zeotype encapsulated metal nanoparticles, the method comprises the steps of: 1) Adding one or more metal precursors to a silica or alumina source; 2) Reducing the one or more metal precursors to form metal nanoparticles on the surface of the silica or alumina source; 3) Passing a gaseous hydrocarbon, alkyl alcohol or alkyl ether over the silica or alumina supported metal nanoparticles to form a carbon template coated zeolite, zeolite-like or zeotype precursor composition; 4a) Adding a structure directing agent to the carbon template coated zeolite, zeolite-like or zeotype precursor composition thereby creating a zeolite, zeolite-like or zeotype gel composition; 4b) Crystallising the zeolite, zeolite-like or zeotype gel composition by subjecting said composition to a hydrothermal treatment; 5) Removing the carbon template and structure directing agent and isolating the resulting zeolite, zeolite-like or zeotype encapsulated metal nanoparticles.

FIELD OF THE INVENTION

The invention concerns a method for making zeolite or zeotypeencapsulated metal nanoparticles and zeolite or zeotype encapsulatedmetal nanoparticles produced by the method.

BACKGROUND OF THE INVENTION

In the view of the current environmental challenges there is an urgentneed to develop a more sustainable chemical industry through moreefficient chemical transformations and by developing new highlyselective and cost-effective catalysts. One approach towards enhancedcatalytic performance of supported metal catalysts is to increase theactive metal surface by synthesizing small metal nanoparticles (often<10 nm in diameter). However, small nanoparticles are often prone tosintering which decreases the catalytic activity over time. Thedevelopment of sinter-stable heterogeneous nano particle catalysts istherefore of great importance.

Zeolites are crystalline alumina silicate materials that exhibit ahighly ordered porous structure with pores of molecular diameter. IUPACidentifies this type of porosity as microporous, as the size of thepores are not wider than 2 nm. The other groups of porosity aremesoporous (pore size between 2-50 nm) and macroporous (pore size largerthan 50 nm). Zeolites consist of tetrahedral TO₄ units (T=Si or Al),which gives the framework an overall composition of TO₂. These materialshave a clear organized framework throughout the crystals, giving rise tohighly ordered pores and a large internal surface area. By replacing asilicon atom with an aluminium atom, it is possible to generate adeficit of charge, which is compensated by a cation located nearby. Thecation is usually an alkali metal (such as sodium), alkali earth metal,or possibly a H⁺ ion. If the cation is a proton, the zeolite becomes astrong Brønsted acid. All these characteristics give rise to a lot ofuses for zeolites.

Today, nearly 60 different natural occurring zeolites are known, while201 can be prepared synthetically [1]. These zeolites have differentstructures, due to different Si—O—Al linkages, and a different number ofSi or Al atoms linked in each “cage”. This also creates different poresystem of one-, two, or three-dimensions in the zeolite.

As the pores are very regular, and around the same size in diameter asmolecules, it is possible for zeolites to function as molecular sieves.Due to their chemical structure and molecular sieve properties, zeolitecatalysts exhibit high selectivity for a variety of chemical reactions.Since most of the surface area and the active sites are within thezeolite, the shape of the pores and channels give rise to shapeselective catalysis. Commonly there is distinguished between three typesof molecular sieving effects:

-   -   1) Reactant shape selectivity: Only molecules small enough can        enter the zeolite pores and undergo chemical transformation or        be adsorbed.    -   2) Product shape selectivity: The size of the pores is too        small, that not all possible products can diffuse out of the        zeolite after reaction. This leads to an increased selectivity        towards smaller molecules or isomers.    -   3) Restricted transition-state shape selectivity: Here the        formation of too large transition state intermediates are        prevented due to zeolite pore size. FIG. 1 illustrates the three        different kinds of shape selectivity.

Zeolite Synthesis

In general, zeolite synthesis is a crystallization process, where silicaand alumina species dissolve and react to give a less solublecrystalline alumina/silicate product. The crystallization process istypically performed in a hydrothermal process where the zeoliteprecursors is put in an autoclave and heated to relatively hightemperatures and autogenous pressures. The high pressure is due to theevaporation of water inside the autoclave, and is very important for thesynthesis. In a typical synthesis the zeolite precursors is dissolved orsuspended in an aqueous solution of a structure directing agent (SDA)and an alkali hydroxide to catalyze the breaking and formation ofchemical bonds [4].

The structure directing agents are almost always organic amine cations.Some of the most commonly used organic structure directing agents aretetramethyl-ammonium (TMA), tetraethylammonium (TEA), andtetrapropylammonium (TPA), though compounds as diverse as Choline,1,6-diaminohexane, and hexanediol have been used. During the zeolitecrystallization process, the zeolites form around molecules of thestructure directing agent. The shape and properties of the structuredirecting agent causes the zeolites forming around it to take a certainshape. Stoichiometric analysis of samples of ZSM-5 has indicated thatone TPA⁺ molecule occupies each intersection between pores in thezeolite [2].

For sources of silicon, mostly sodium silicate, fumed silica ortetraethoxy ortho-silicate is used, while sodium aluminate, aluminumnitrate or -chloride are typical sources of aluminum [3]. The mixture ofzeolite precursors or zeolite gel is then transferred to an autoclaveand heated to a predetermined temperature, often between 120-200° C.Within days, possible weeks, the precursors begin to crystallize andform the zeolite. After the synthesis, the autoclave is cooled to roomtemperature, and the zeolite material is washed with water and isolatedby filtration or centrifugation. The zeolite is then calcined at around500-600° C. to remove residual SDA and framework water. At last thezeolite can be ion exchanged. This can either be done to introducehydrons, alkali metal, alkali earth metal, lanthanoid or transitionmetal cations.

One method to produce a porous system inside a zeolite is templating.Several types of templates have been utilised for the introduction ofpores in zeolites. One of them; hard templating applies a solid materialto generate a porous system in addition to the inherent micropores. Thismethod has proved to be very effective and a highly versatile approach.Templates include organic aerogels, polymers, and carbon in differentforms. Here, only carbon will be discussed. One of the well-knownmethods is the crystallization of zeolite gel in porous carbonparticles. If the amount of synthesis gel relative to the carbontemplate is sufficient, the zeolite crystals continue to grow afternucleation in the cavities of the carbon. This will allow the zeolitecrystal to encapsulate the carbon. Combustion of the carbon particlesembedded in the zeolite crystal, will lead to the formation of mesopores[37]. Several types of carbon nanoparticles have been used [38],including carbon nanotubes [39] and nanofibers.

In 1983 Taramasso et al. incorporated titanium ions into silicalite-1(denominated as TS-1) [56]. The incorporation of titanium, is aisomorphous substitution in the MFI lattice of the silicalite-1. Thepresence of a titanium atom gave rise to different catalytic properties,than the selective acid catalytic properties displayed by conventionalalumina silicate zeolites. The TS-1 has been found useful in selectiveoxidation reactions, such as the hydroxylation of phenols, epoxidationof alkenes, and ammoxidation of ketones [57-61].

Encapsulation of metal nanoparticles in a zeolite structure can improvethe physical properties of the zeolite, but in addition to that; theencapsulated metal nanoparticles can have catalytically propertiesthemselves. As a further potential advantage, the encapsulation canprotect the individual nanoparticles from contact with othernanoparticles, thereby preventing sintering of the nanoparticles whenthese are subjected to elevated temperatures.

In spite of the great technological, environmental and economicinterests, general methods for the stabilization of metal nanoparticlesagainst sintering are far from being fully developed, although for somespecific systems it has been achieved by optimizing the interaction ofnanoparticles with a support material or by encapsulation of the metalparticles [52, 93, 94]. However, these known catalytic systems are ingeneral very expensive and difficult to synthesize and they cannot beproduced in industrial scale. Nanoparticles encapsulated in zeolite-likestructure have only been reported in a handful of papers [46, 52,95-99].

The encapsulation of nanoparticles is an area of increasing interest.This is a possible solution to the widely known problem of deactivationdue to sintering. Several methods have been developed to producesinter-stable nanoparticle catalyst, including encapsulating inmesoporous silica matrix or by using a protective shell [45-48]. None ofthese materials are however shape-selective. By encapsulating metalnanoparticles in a zeolite matrix, on the other hand, shape selectivecatalysis is possible. In addition, the thermal stability of zeolitesand high surface area, makes zeolites particularly useful for thisapplication. Post treatment deposition of nanoparticles inside zeoliteshas been reported in literature [49-51]. A limitation of these methodsis however that they require zeolites containing cages.

By post-synthesis treatments the nanoparticles are in the cages and/orin the pores of the zeolite and it can be difficult to control the sizeand location of the nanoparticles. Both Laursen et al. and Tøjholt etal. have successfully synthesised a MFI zeolite containing goldnanoparticles (size 1-3 nm), which showed to be highly stably versussintering [52, 53]. In addition, the gold nanoparticles were onlyaccessible through the micropores of the zeolite. The synthesis ishowever difficult, and requires a lot of exotic materials and time.

So, despite the growing demand, a fast, efficient and economicallyprocess for manufacturing zeolite or zeotype encapsulated metalnanoparticles which are sinter-resistant that can be scaled up forindustrial application has not yet been reported.

SUMMARY OF THE INVENTION

The present invention relates to method for producing zeolite,zeolite-like or zeotype encapsulated metal nanoparticles, the methodcomprises the steps of:

-   -   1) Adding one or more metal precursors to a silica or alumina        source;    -   2) Reducing the one or more metal precursors to form metal        nanoparticles on the surface of the silica or alumina source;    -   3) Passing a gaseous hydrocarbon, alkyl alcohol or alkyl ether        over the silica or alumina supported metal nanoparticles to form        a carbon template coated zeolite, zeolite-like or zeotype        precursor composition;    -   4a) Adding a structure directing agent to the carbon template        coated zeolite, zeolite-like or zeotype precursor composition        thereby creating a zeolite, zeolite-like or zeotype gel        composition;    -   4b) Crystallising the zeolite, zeolite-like or zeotype gel        composition by subjecting said composition to a hydrothermal        treatment;    -   5) Removing the carbon template and structure directing agent        and isolating the resulting zeolite, zeolite-like or zeotype        encapsulated metal nanoparticles.

The present invention also relates to a zeolite, zeolite-like or zeotypeencapsulated metal nanoparticles manufactured by the method according tothe present invention.

FIGURES

FIG. 1: The three types of shape selectivity [3].

FIG. 2a : Overview of principles of zeolite synthesis.

FIG. 2b : Overview of developed procedure for the synthesis of carbontemplate mesoporous zeolites and sintering stable heterogeneousnanoparticle catalysts.

FIG. 3: The six types of isotherms as classified by IUPAC [80].

FIG. 4: XRPD patterns of conventional (TS-1), carbon-templated (cTS-1),desilicated (dTS-1), and TS-1 subjected to both carbon-templating anddesilication (cdTS-1).

FIG. 5: XRPD pattern of Ni-0.74-TS-1 synthesized using propene.

FIG. 6: Scanning electron microscope images of conventional andmesoporous TS-1,plus their desilicated counterparts.

FIG. 7: Scanning electron microscope images of silica samples preparedby coking of nickel and iron nanoparticles.

FIG. 8: Scanning electron microscope images of TS-1 prepared with nickelnanoparticles.

FIG. 9: Nitrogen adsorption/desorption isotherms of conventional andmesoporous samples. (□) TS-1, (∘) dTS-1, (⋄) cTS-1, (Δ) cdTS-1. Blanksymbols represent the adsorption isotherm, while filled represent thedesorption. (please note the offset).

FIG. 10: BJH pore size distribution based on the desorption isotherms.(□) TS-1, (∘) dTS-1, (⋄) cTS-1, (Δ) cdTS-1.

FIG. 11: Nitrogen adsorption/desorption isotherms of Ni-0.74-TS-1.

FIG. 12: BJH pore size distribution of Ni-0.74-TS-1 based on thedesorption isotherms.

FIG. 13: UV-Vis spectra of TS-1 and its mesoporous derivates.

FIG. 14: UV-Vis spectra of Ni-0.74-TS-1 and conventional TS-1.

FIG. 15: Transmission electron microscopy of a mesoporous MFI zeolitesynthesized using methane, where the material is heated to 550° C. underargon before methane gas is added.

FIG. 16: Scanning electron microscope images of a MFI zeolitesynthesized using methane, where the material is heated to 700° C. underargon before methane gas is added.

FIGS. 17a -b: XRPD pattern of MFI synthesized using methane, where FIG.17a represents a synthesis method, where the material is heated to 550°C. under argon before methane gas is added and FIG. 17b represents asynthesis method, where the material is heated to 700° C. under argonbefore methane gas is added.

DETAILED DESCRIPTION OF THE INVENTION

In the following detailed description of the invention, reference ismade to the examples, including tables and figures.

In this application a method for producing zeolite, zeolite-like orzeotype encapsulated metal nanoparticles is presented. This is a newmethod to synthesize zeolite, zeolite-like or zeotype encapsulated metalnanoparticles where the carbon template is generated by a direct cokingprocess facilitated by pre-formed metal nanoparticles on thesilica/aluminium source.

The invention therefore relates to a method for producing zeolite,zeolite-like or zeotype encapsulated metal nanoparticles, the methodcomprises the steps of:

-   -   1) Adding one or more metal precursors to a silica or alumina        source;    -   2) Reducing the one or more metal precursors to form metal        nanoparticles on the surface of the silica or alumina source;    -   3) Passing a gaseous hydrocarbon, alkyl alcohol or alkyl ether        over the silica or alumina supported metal nanoparticles to form        a carbon template coated zeolite, zeolite-like or zeotype        precursor composition;    -   4a) Adding a structure directing agent to the carbon template        coated zeolite, zeolite-like or zeotype precursor composition        thereby creating a zeolite, zeolite-like or zeotype gel        composition;    -   4b) Crystallising the zeolite, zeolite-like or zeotype gel        composition by subjecting said composition to a hydrothermal        treatment;    -   5) Removing the carbon template and structure directing agent        and isolating the resulting zeolite, zeolite-like or zeotype        encapsulated metal nanoparticles.

The metal nanoparticles are still present within each single crystal ofthe zeolite after synthesis. When the carbon template has been removedby calcinations from the zeolite structure the nanoparticles areindividually encapsulated within the created pores or cavities of thezeolite structure, so that the individual nanoparticles are protectedfrom contact with other nanoparticles, thereby preventing sintering ofthe nanoparticles when these are subjected to elevated temperatures.

The zeolite, zeolite-like or zeotype encapsulated metal nanoparticlesare preferably sinter stable or sinter resistant.

By encapsulating metal nanoparticles in a zeolite matrix, shapeselective catalysis is possible.

By encapsulation, the metal nanoparticles are immobilised and sustainedin the entire zeolite crystals, and thus more stable towards sintering.The nanoparticles are accessible through the framework of pores whichact as molecular sieves.

The novel method can be used to synthesize sintering stableheterogeneous nanoparticle catalysts useful for environmental protectionand production of chemicals. The zeolite-based catalysts containingmetal nanoparticles are synthesized according to the approach depictedin FIG. 2b . The hydrocarbon gas alkyl alcohol or alkyl ether which isemployed in step 3 decomposes on the metal surface to leave a protectivelayer of carbon around the metal nanoparticles. It is expected that thisnovel synthesis method can improve the current synthesis of encapsulatedmetal nanoparticles in zeolites.

The encapsulation of metal nanoparticles within the zeolite structureinhibits sintering, thereby preserving their high surface area requiredfor the effective catalytic activity. This novel approach forpreparation of sintering stable heterogeneous nanoparticle catalysts israther simple and can be used to develop novel automotive exhaustcatalyst. Moreover, it is also the more general method for thestabilization of metal nanoparticles against sintering which could finduse in the chemical and pharmaceutical industry. For example, theheterogeneous gold, silver and platinum nanoparticle catalysts areactive and selective catalysts for several oxidation reactions.

The method of the invention is based on carbon templating and originatesfrom the desire to develop a fast, efficient and cheap alternativemethod that can be scaled up for industrial application more easily thanthe known sucrose method [41]. An overview of this synthesis ispresented in FIG. 2 b.

Different zeolite structures (framework) are suitable for the abovemethod of production. The zeolite structure can be zeolite beta (BEA), Y(FAU), ZSM-5 (MFI), ZSM-11 (MEL) or ZSM-12 (MTW).

Throughout the description, when zeolites are mentioned this is meant tocomprise zeolites, zeolite-like materials and zeotypes unless otherwisespecifically mentioned.

By the term zeolite-like is meant non-silicon comprising material.Examples of zeolite-like materials are non-silicon comprising materialssuch as aluminium phosphate (AlPO4) molecular sieves, known as AlPO's.The phosphorous compound can be selected from the group consisting ofphosphoric acid, phosphate salts and mixtures thereof. By the term“phosphate salts” is meant salts of phosphates, monohydrogen phosphatesand dihydrogen phosphates.

By zeolite, zeolite-like and zeotype particle is meant zeolite,zeolite-like and zeotype crystal or zeolite, zeolite-like and zeotypematerial.

“Metal nanoparticles” also comprises mixtures of metals nanoparticles.

By metal nanoparticles is also meant metal oxide nanoparticles and metalnitrate nanoparticles. The metal or mixture of metal precursors mightform into the respective oxides or nitrates. This can happen eitherduring the manufacturing process or in the end product.

Possible silica sources for zeolites may be bulk silica of differentquality and alumina contamination, including pure silica, fumed silica,sodium silicate or other soluble silicate salts, precipitated silica,tetraethyl orthosilicate and other alkoxy-silicates, silicic acid, etc.

Possible aluminium sources for zeolites may be aluminum nitrate,aluminum sulphate, aluminum phosphate, sodium aluminate ect.

The inherent micropores in the zeolite structure are also here calledprimary porosity whereas the ekstra pores created by the method of thepresent invention are referred to as secondary porosity. This secondaryporosity can both be micropores or mesopores.

The first step in the process is to add a metal or a mixture of metalprecursors to a silica/alumina precursor. In one embodiment the firststep is performed at elevated temperatures such as from 50° C. to 150°C., such as around 80° C.

The metal precursors can be added by grinding, impregnation,co-precipitation, deposition-precipitation or chemical vapor deposition.

Impregnation: a solution, e.g. an aqueous or alcoholic solution of oneor several transition metal precursors is applied to a silica/aluminasource. The solution is dryed, e.g. in an oven at 80° C. overnight,whereby water is evaporated and left is the metal on the surface of thesilica/alumina source.

Deposition Precipitation: silica and the metal or mixture of metals ismixed together in a solution. By changing pH or adding chemicals, e.g.H₂O₂, the character of the metal change to another compound and depositon the silica.

Chemical Vapour Deposition: The metal or mixture of metals can be in agas phase or liquid phase. If the metal is in a liquid phase the liquidis heated to the boiling point and lead over the silica where it isdeposited. If the metal is in the gas phase, the gas is lead over thesilica where it is deposited.

In one embodiment nickelparticles are made volatile by CO and carbonylcompound are created, which are deposited on the silica and createscarbon nanotubes.

In one embodiment of the method for producing zeolite, zeolite-like orzeotype encapsulated metal nanoparticles the one or more metal(s) isselected from the group consisting of group 4 elements, group 6elements, group 7 elements, group 8 elements, group 9 elements, group 10elements, group 11 elements or group 12 elements or mixtures thereof.The group elements are defined by the new IUPAC numbering.

In one embodiment of the method the one or more metal(s) is selectedfrom the group consisting of titanium, osmium, iridium, platinum,ruthenium, palladium, rhodium, rhenium, copper, nickel, iron, cobalt,silver, gold, cadmium, molybdenium or mixtures thereof. In oneembodiment the metal is nickel.

In one embodiment of the method for producing zeolite, zeolite-like orzeotype encapsulated metal nanoparticles the first step is performed ina liquid phase, e.g. in an aqueous or alcoholic solution, in a gas phaseor in a solid phase. The aqueous or alcoholic solution of of the one ormore metal precursors could comprise nitrates, carbonates, acetatessulphates orchlorides.

In another embodiment, the first step in the process involvesimpregnating a silica or alumina precursor with an aqueous or alcoholicsolution of one or more transition metal precursors. The possible metalsespecially include Fe, Co, Ni, Cu, Ru, Rh, Pd, Ag, Pt, Au, Mo, andmixtures thereof. The possible metal precursor could be nitrates,carbonates, acetates, sulfates, chlorides, carbonyls, and several othercheap and readily available chemicals.

The possible metal can also be a metal alloy such as gold-platinum,copper-palladium, ruthenium-copper, platinum-iridium,platinum-palladium, platinum-ruthenium, cobalt-molybdenum,nickel-molybdenum, or palladium-gold, where one of the metals in themetal alloy can be present in an amount of from 1 to 50%. The optimalweight ratio between the metals in the alloy depends on the metal alloy.

The second step in the process involves reducing the one or more metalprecursors to form metal nanoparticles on the surface of the silica oralumina source. The metal precursors is reduced in a reducingatmosphere, for instance in a stream of hydrogen gas, or decomposed by athermal treatment to give the corresponding transition metalnanoparticles. The transition metal nanoparticles can also be in theform of metal oxide nanoparticles or metal nitrate nanoparticles. Thisreduction step is in one embodiment performed at elevated temperatures,e.g. from 200 to 800° C. such as from 200 to 700° C., or such as from200 to 600° C.

The third step in the process involves passing a gaseous hydrocarbon,alkyl alcohol or alkyl ether over the silica or alumina source with theimpregnated metal nanoparticles, forming a zeolite precursor compositioncomprising carbon coated metal nanoparticles. The physical shape of thecarbon (also called the carbon template) coating the nanoparticles canvary depending on the process conditions. In one embodiment the carbonis in the form of whiskers (nanotubes). In another embodiment the carbonis in the form of nanofibers. In another embodiment the carbon is in theform of spheres encircling the metal nanoparticles.

In one embodiment the flow of gaseous hydrocarbon, alkyl alcohol oralkyl ether is in the range of 20 to 500 ml/min, 20 to 400 ml/min, 100to 400 ml/min, 30 to 100 ml/min, 50 to 90 ml/min, 50 to 70 ml/min or 60to 70 ml/min.

In one embodiment, the third step of the process involves heating thesilica or alumina and metal nanoparticles to 200-1100° C., such as from200-800° C. or from 300-1100° C.

In separate embodiments the hydrocarbon is selected from aliphatichydrocarbons having 1 to 8 carbon atoms, having 1 to 3 carbon atoms,alkenes having 2 to 6 carbon atoms, aromatic hydrocarbons having 6 to 10carbon atoms and cyclic hydrocarbons having 3 to 8 carbon atoms.

In one embodiment the hydrocarbon gas is selected from methane, propene,xylene, methane or benzene.

In other separate embodiments the alkyl alcohol is selected fromaliphatic alcohols having 1 to 8 carbon atoms, or having 1 to 3 carbonatoms.

In other separate embodiments the alkyl ether is selected from aliphaticethers having 2 to 8 carbon atoms, or having 2 to 4 carbon atoms.

In a specific embodiment the alkyl ether is DME (dimethylether).

In one embodiment the flow of gaseous hydrocarbon, alkyl alcohol oralkyl ether is applied for around 1-5 hours, e.g. 2 hours.

In one embodiment, the third step of the process involves that thesilica or alumina and metal nanoparticles is heated (maybe 300-1100° C.)in a stream of a simple hydrocarbon gas (1-8 carbon atoms or cyclichydrocarbons) that decomposes on the metal surface to leave the carbontemplate on the zeolite precursor composition. The layer of carbonprotects the nanoparticles in the relatively harsh reaction(temperature, pressure, alkaline) that are necessary to grow thezeolite.

The fourth step involves two steps; step 4a is adding a structuredirecting agent to the carbon template coated zeolite, zeolite-like orzeotype precursor composition thereby creating a zeolite, zeolite-likeor zeotype gel composition; and step 4b is crstallization of thezeolite, zeolite-like or zeotype gel composition by subjecting thezeolite, zeolite-like or zeotype gel composition to a hydrothermaltreatment.

During this step 4, the silica/aluminium is dissolved in an aqueousalkaline media creating a supersaturated solution from which the zeoliteis formed around the carbon template in the presence of a structuredirecting agent (SDA), preferably a quaternary ammonium salt such asTPAOH (tetrapropylammonium hydroxide) or TBAOH (tetrabutylammoniumhydroxide). This creates an initial, amorphous zeolite gel, which in asubsequent hydrothermal step is transformed into the crystallinezeolite. The hydrothermal process is often performed under elevatedtemperatures between 70 and 300° C., preferably at 180° C., andautogeneous pressure in an autoclave or open flask for 24 hours or more.

A hydrothermal process is a technique of crystallizing substances fromhigh-temperature aqueous solutions at high vapour pressure.

In one or more embodiments, the carbon template coated zeolite,zeolite-like or zeotype precursor composition of step 3 is used directlyin step 4a without removing the silica or alumina source. In this way,the silica or alumina source is reused in the following process, whichreduces the production cost compared to alternative processes, where itis removed and only the carbon skeleton is used in the further processas seen in e.g. A. H. Janssen et al, Microporous and MesoporousMaterials 65 (2003), page 59-75. Further, by reusing the silica oralumina source, the method is simplified.

In a specific embodiment, the fourth step comprises a hydrothermaltreatment of the initially formed zeolite gel wherein the gel is heatedto temperatures between 70 and 300° C., preferably at 180° C. Inaddition it may be under an autogeneous pressure in an autoclave or openflask for 24 hours or more.

In one embodiment the method of producing zeolite or zeotypeencapsulated metal nanoparticles comprises adding an Al, Sn, Ti, Zr orGe source during step 4a. The source may be an Al³⁺, Sn²⁺, Sn⁴⁺, Ti⁴⁺,Zr or Ge source. Sources of Titanium could be e.g. titanium chlorides,titanium sulphates, titanium alkoxides e.g. TEOT (tetraethylorthotitanate) and TBOT (tetrabutyl orthotitanat). Sources of aluminiumcould be aluminum nitrate, aluminum sulphate, aluminum phosphate, sodiumaluminate ect. Sources of tin could be tin chlorides, tin oxides orsolid tin dissolved in hydrochloric acid. Sources of zirconia could bezirconia chloride or zirconia oxide. If an aluminium source was used instep 1 in the process instead of a silica source, then a silica sourceshould be applied at this step. The source of silica is bulk silica ofdifferent quality and alumina contamination, including pure silica,fumed silica, sodium silicate or precipitated silica, tetraethylorthosilicate ect.

The source of Al³⁺, Sn²⁺, Sn⁴⁺, Ti⁴⁺, Zr or Ge will be part of theframework in the crystal structure. Therefore, Ti-zeotype particles,Sn-zeotype particle, Zr-zeotype particle or Ge-zeotype particles can bemanufactured by the present method.

In the fifth step the catalyst is washed, dried and calcined in air atabove 300° C., preferably between 300-700° C., preferably between400-700° C. to remove the structure directing agent and the carbontemplate. More preferably a controlled combustion is conducted bycalcination the crystalized zeolite in air at 550° C. The combustion isconducted for e.g. 24 hours or 20 hours. Upon removal of the carbontemplate, by calcination, the zeolite crystals obtain a secondaryporosity, in addition to the inherent zeolite microporous system. Theporosity can be modified by changing the type and amount of carbon.

According to the present invention, the metal nanoparticles previouslysupporting the growth of carbon templates (whiskers, nanotubes etc)during the third step of the process are left behind in the secondaryporosity of the zeolites after the fifth step has been carried out.These metal nanoparticles are homogeneously distributed throughout thecrystalline zeolite structure and are further individually shielded fromphysical contact with other metal nanoparticles hosted in the zeolite bythe walls of the formed pores. The metal nanoparticles remain accessiblethrough the porous structure of the zeolites, however, but are thusprotected from sintering with other nanoparticles at elevatedtemperatures due to said physical separation.

The calcination procedure conducted in step 5 is expected to remove thecarbon template and remaining amounts of the structure directing agent.However, under certain combinations of reaction parameters the isolatedencapsulated metal nanoparticles may still contain traces of carbontrapped in the zeolite structure which may influence the eventualactivity and/or selectivity of the metal nanoparticles.

In the following one possible method is outlined. The first stepinvolves that an aqueous solution of a metal nitrate is impregnated onthe silica. The metal nitrate is then reduced in a hydrogen stream toform metal nanoparticles. Subsequently, the gas flow is exchanged and acarbon gas, e.g. propene gas is passed over the sample. Depending on thenature of the metal nanoparticles, the time of exposure to thehydrocarbon gas, the temperature, the carbon gas, e.g. propene may coverand encapsulate the metal nanoparticles or deposit as carbon [42, 43].After this procedure, the zeolite precursor is mixed with a structuringdirecting agent (SDA) and OH⁻ and put in a Teflon beaker inside aTeflon-lined autoclave containing a sufficient amount of water togenerate saturated steam and heated to e.g. 180° C. for e.g. 72 hours.After the hydrothermal treatment, the carbon template is removed bycombustion. This will lead to uniformed micropores or mesopores in thezeolite, which are modifiable by increasing or decreasing thenanoparticle size.

In one embodiment of the method the carbon template is shaped as carbonnanotubes.

Carbon formation in the form of whisker carbon is a very commonphenomenon with e.g. nickel nanoparticles [42, 43]. This might resort toa larger amount of carbon formation than expected if the nanoparticleswhere simply encapsulated. The length, width and amount of carbon, e.g.in the form of whiskers, can be tuned by changing the differentparameters, such as gas, temperature and time.

In one embodiment of the method the one or more metal precursors isloaded to the silica or alumina in an amount of 0.5 to 20 wt %, from 0.5to 5 wt %, from 0.5 to 2 wt %, or around 1 wt % during step 1.

In one embodiment of the method the zeolite precursor has acarbon-to-silica ratio of from 0.30 to 2.00 w/w, 0.30 to 1.00 w/w, 1.00to 2.00 w/w or from 0.34 to 0.75 w/w.

In one embodiment of the method the zeolite precursor has acarbon-to-alumina ratio of from 0.30 to 2.00 w/w, 0.30 to 1.00 w/w, 1.00to 2.00 w/w or from 0.34 to 0.75 w/w.

EDS analysis of the calcined zeolite showed presence of nickel,titanium, oxygen and silicon.

The present invention also relates to a zeolite, zeolite-like or zeotypeencapsulated metal nanoparticles manufactured by the method according tothe present invention.

The physical and chemical properties of the zeolite material aremodified by having the encapsulated nanoparticles within the pore systemof the zeolite crystal.

In one embodiment, the encapsulated metal nanoparticles aresinter-resistant.

In one embodiment the particle is a hierarchical mesoporous zeolite,zeolite-like or zeotype particle.

In one embodiment the particles comprises mesopores in the range from 2to 50 nm, from 5 to 30 nm, from 10 to 25 nm, from 15 to 25 nm, from 18to 22 nm, from 19 to 21 nm or around 20 nm. In one embodiment theparticles comprises mesopores having sizes around 10 nm.

In one embodiment the zeolite particles comprises micropores in therange from 0.1 to 2 nm, from 1 to 2 nm or around 2 nm.

In one embodiment the encapsulated metal nanoparticles comprise one ormore metal(s) selected from the group consisting of group 4 elements,group 6 elements, group 7 elements, group 8 elements, group 9 elements,group 10 elements, group 11 elements or group 12 elements or mixturesthereof. The group elements are defined by the new IUPAC numbering.

In one embodiment the encapsulated metal nanoparticles comprise one ormore metal(s) selected from the group consisting of titanium, osmium,iridium, platinum, ruthenium, palladium, rhodium, rhenium, copper,nickel, iron, cobalt, silver, gold, cadmium, molybdenium or mixturesthereof. In one embodiment the metal is nickel.

In one embodiment the size of the crystal structure are in the range of1.0 to 2.5 μm.

In one embodiment the metal nanoparticles are immobilized in the zeoliteor zeotype.

In one embodiment the zeolite, zeolite-like or zeotype encapsulatedmetal nanoparticles comprise an Al, Sn, Ti, Zr or Ge source in theframework of the crystal structure. The source may be an Al³⁺, Sn²⁺,Sn⁴⁺, Ti⁴⁺, Zr or Ge source.The source of Al³⁺, Sn²⁺, Se, Ti⁴⁺, Zr or Gewill be part of the framework in the crystal structure. Therefore, theinvention also comprise Ti-zeotype particles, Sn-zeotype particle,Zr-zeotype particle or Ge-zeotype particles manufactured by the presentmethod.

In one embodiment the amount of metal nanoparticles are in the range of0.1 to 25 wt %, in the range from 0.5 to 20 wt %, from 0.5 to 10 wt %,from 0.5 to 5%, from 1.0 to 5 wt %, from 1 to 2 wt %, or around 1 wt %.

The amount of metal nanoparticles in the crystallised zeolite structureis preferably more than 80% of the metal loading.

In one embodiment the zeolite, zeolite-like or zeotype particle has a Vpvalue in the range of 0.300 to 0.500 cm³/g, 0.300 to 0.400 cm³/g oraround 0.320 cm³/g, or around 0.450 cm³/g.

In one embodiment the zeolite, zeolite-like or zeotype particle has anexternal surface area in the range of 100-400 m²/g, or around 170 to 200m²/g or around 190 m²/g.

In one embodiment the zeolite, zeolite-like or zeotype particle has aBET surface area of 300 to 500 m²/g or 350 to 400 m²/g.

The zeolite, zeolite-like or zeotype encapsulated nanoparticles of theinvention can be used as catalytic material for chemical reactions.

The invention also relates to the use of the zeolite, zeolite-like orzeotype encapsulated metal nanoparticles of the present invention inshape-selective catalysis.

Experimental Details

Methods for Characterisation—X-ray Powder Diffraction XRPD is a widelyused analytic method for structural characterization of crystallinematerials. It is used to identify crystal structure and detect impurityphases. The method is based on diffraction, which occurs when anincident radiation interacts with an ordered solid and the wavelength ofthe electron magnetic radiation is in the same order as the distancebetween the crystal planes. Most often, the zeolite is analysed in theform of a powder and the obtained powder X-ray diffractogram can be usedas a fingerprint unique to the particullar crystalline phase. Due to thesmall amount of titanium in the sample, it will be difficult to discernby XRPD, whether TiO₂ has formed. X-ray powder diffraction patterns(XRPD) was measured in transmission mode using Cu—Kα radiation from afocusing quartz monochromator and a HUBER G670 Guinier camara.

Methods for Characterisation—Scanning Electron Microscopy (SEM)

This analytic technique uses a finely focused high energy beam ofelectrons are is directed onto the surface of a sample. The electronswhich are reflected by the surface and emitted secondary electrons, aredetected to give a map of the surface topography of the sample. Thesamples may need to be applied with a conductive coating such as gold orgraphite, to hinder local surface charging which leads to a decreasedquality of SEM images [79].

Methods for Characterisation—Transmission Electron Microscopy (TEM)

TEM is a microscopy technique in which a beam of electrons istransmitted through an ultra-thin specimen, interacting with thespecimen as it passes through. An image is formed from the interactionof the electrons transmitted through the specimen; the image ismagnified and focused onto an imaging device, such as a fluorescentscreen, on a layer of photographic film, or to be detected by a sensorsuch as a CCD camera.

Methods for Characterisation—Energy Dispersive X-ray Spectroscopy

In electron microscopy, the elements present in the sample emitcharacteristic X-rays due to the incident electron beam. These X-rayscan be analysed to give a spectrum, and from there give both qualitativeand quantitative results of the elements present [79]. Severalprecautions must however be made, as it is nigh impossible to getaccurate quantitative results with this method on samples such aszeolites. This is because the accuracy of the spectrum is affected bythe nature of the sample. X-rays are generated by any atom in the samplethat is sufficiently excited by the incident electron beam. The X-raysare emitted in any direction, and so they may not all escape the sample.The likelihood of a X-ray escaping the sample, depends on the energy ofthe X-ray and the amount and density of material it has to pass through.This can result in reduced accuracy in porous and rough samples. Aszeolites present are porous, the EDS results must be interpreted withcaution, and are therefore only used qualitatively.SEM and EDS analysiswere performed on a Quanta 200 ESEM FEG. The calcined zeolite sampleswere placed on a carbon film.

Methods for Characterisation—Nitrogen Phvsisorption

Key parameters for a solid catalyst is the accessibilty of the activesites for reactants. A conventional way of measuring this is byphysisorption of nitrogen gas at 77 K. This method provides informationon both surface area and pore size distribution in the micro-, meso- andmacroporous range. The method is a stepwise adsorption of N₂ which firstforms a monolayer, as the pressure of N₂ increases multi layers begin toform. The N₂ physisorption isotherms generated are very distinct, andclassified into six types by IUPAC [80] which are presented in FIG. 3.Nitrogen physisorption of microporous solids, such as zeolites, resulttypically in Type I isotherms. They are characterised by the limitinguptake, which happens at relative low pressure and is controlled by theaccessible micropore volume, and not the internal surface area. Type IVisotherms are most common when analysing mesoporous materials. Thehysteresis loop between the adsorption and desorption branches, is avery characteristic feature for this type of isotherm, and is attributedto capillary condensation taking place in mesopores. Type II, III, V andVI are not commonly observed for zeolite materials, since they aretypical for non-porous, macroporous or materials with weak forces ofadsorption [80].

Nitrogen adsorption and desorption measurements were performed at liquidnitrogen temperature (77 K) on a Micromeritics ASAP 2420. The sampleswere outgassed in vacuum at 300° C., 16 hours prior to measurement. Thetotal surface areas were calculated according to the BET method. Poresize distributions were calculated with BJH method. External surfacearea, micropore area and micropore volume were determined by t-plotmethods in the desorption branch. Total pore volume was calculated forpores around 80 nm width at p/p0=0.97.

Methods for Characterisation—Diffuse Reflectance UV-Vis Spectroscopy

By exposing molecules to radiation in the ultraviolet-visible (UV-Vis)spectral region, spectroscopy can be applied to determine theconcentration of an analyte. However, important characteristics of thesample are obtainable. It is possible to detect and determine thecoordination environment of d-d transitions in the sample, andmetal-ligand complexes due to the specific energy required to excitethem. However, in the case of powdered catalyst samples, the incidentlight can not penetrate the sample and is almost completely diffused. Itis therefore not possible to use transmission spectroscopy, insteaddiffuse reflectance (DR) spectroscopy has to be applied. Overall, thismethod can serve as a great asset in determining which titanium speciesis present in the produced catalysts. DR UV-Vis spectra were obtainedwith a CARY 5000 spectrometer employing spectralon® as internalstandard.

Materials

Mesoporous silica (Merck, silica gel 100, particle size 0.063-0.200 mm,pore diameter 15 nm, pore volume 1.15 ml/g), was used for the synthesisof mesoporous zeolites involving metal nanoparticles. The silica weredried at 80° C. for 24 hours prior to use. All other reagents were ofreagent grade and used without further purifications:tetraethylorthosilicate (TEOS, 98 wt %, Aldrich),tetraethylorthotitanate (TEOT, 98 wt %, Aldrich), tetrapropylammoniumhydroxide (TPAOH, 40 wt %, Fluka), hydrogen peroxide (H₂O₂, 40 wt %,Aldrich).

Synthesis—Propene Based Method

The zeolites prepared by the new synthesis method disclosed in thisapplication may be prepared by the following method using propene toform the carbon template coated zeolite, zeolite-like or zeotypeprecursor composition: First, 2.5 grams of silica is impregnated toincipient wetness with a metal nitrate solution, eg. nickel nitrate.This is allowed to stand at 80° C. overnight. The solid is subsequentlyplaced in a tube oven and heated to 600° C. in argon flow. A gas mixtureof 10% hydrogen in nitrogen is then led over for a total of 4 hours. Thetemperature is afterwards reduced to 550° C. under argon atmosphere. Asan alternative to reducing the temperature to 550° C. under argonatmosphere, it may be increased to 700° C. still under argon atmosphere.

Propene gas is subsequently applied for 2 hours, afterwards a low flowof argon is led over, while the sample is allowed to cool off. Puresilica did not change colour during the procedure, while both nickel-and iron nitrate on silica were completely black after the treatment.

A mixture of 16.915 g 20% TPAOH, 4.25 ml water, 0.265 g NaOH and 0.095 gTEOT is prepared and stirred until a clear solution was obtained. Thesilica-carbon composite is added and left for 1 hour. The gel is thenintroduced into a stainless steel autoclave which is heated to 180° C.for 72 hours. Afterwards it is filtrated until the rinse water isneutral. The solid is left overnight at room temperature, followed bycalcination at 550° C. for 24 hours. Zeolites made by this method arenominated Metal-C/SiO2 ratio-TS-1, e.g. Ni-0.74-TS-1.

The above synthesized zeolite is in the following compared to othermesoporous catalysts prepared through carbon templating and desilication(results presented in FIGS. 4-6 and 8-14). This is done to determine theinfluence the synthesis method has on active species in the catalyst, aswell as the effect on the external surface area, and the ability tointroduce mesoporosity in addition to the microporosity found inconventional zeolites.

In the following, conventional TS-1 catalysts are denoted TS-1 andmesoporous carbon-templated TS-1 (1% Ti) are denoted cTS-1. Aconventional TS-1 that has been desilicated is denoted dTS-1 and TS-1that has been prepared with BP-2000 and desilicated is named cdTS-1.

Characterization of Catalysts—Carbon Uptake with Propene Method

Several experiments were done to test the carbon loading with differentparameters. After the carbon loading, several were synthesised to eitherHZSM-5, TS-1 or both. Table 1 shows the carbon uptake in acarbon-to-silica ratio (on weight basis) with different metals andparameters. Pure silica took up no amount of carbon, which also wasproven by the absence of colour change after the propene procedure. Thefollowing zeolite synthesis was abandoned, as this would only create aconventional zeolite. The carbon uptake on nickel-SiO₂ was proven to bemodifiable by both changing the metal loading and the flow of propene.An increase in nickel loading, also increased the carbon uptake, with alinear correlation. By changing the flow of propene, it was possible tomodify the carbon uptake to some extent. An increase in flow from 51ml/min to 67 ml/min resulted in a raise of C/SiO₂ ratio from 0.34 to0.74. This was not increased further by another raise in flow speed.Iron showed a very limited uptake with a C/SiO₂ ratio of 0.03. Thesilica was black after the propene treatment, confirming the uptake ofcarbon.

TABLE 1 Carbon uptake of silica with different metal loading and propeneflow. Metal Propene C/SiO₂ Samples Loading [wt %] Flow [ml/min] Ratio[w/w] SiO₂ — 67 0 Ni—SiO₂ 1% 51 0.34 Ni—SiO₂ 1% 67 0.74 Ni—SiO₂ 1% 850.75 Ni—SiO₂ 2% 67 1.18 Ni—SiO₂ 5% 67 2.13 Fe—SiO₂ 1% 67 0.03

Characterization of Catalysts—XRPD

For comparison of crystallinity of the zeolite catalysts, XRPD patternswere recorded after synthesis and subsequent calcination. Patterns forall synthesised TS-1 catalysts are presented in FIG. 4. It is clear thatthe zeolite samples contain highly crystalline structure, with noimpurities or amorphous phase present. It is difficult to discern iftitanium is present in other confirmations than inside the framework, asthe titanium content is very low. In addition, all patterns match thepattern of silicalite-1, confirming the MFI structure. The Ni-0.74-TS-1catalyst produced by the synthesis method disclosed in this application(nickel-propene method), also underwent XRPD analysis. The result ispresent in FIG. 5. The catalyst exhibit the same characteristic patternas samples with MFI structure. In addition, no amorphous phase orimpurities were found present, and the sample was highly crystalline.

Characterization of Catalysts—Scanning Electron Microscopy (SEM)

All synthesised catalyst underwent analysis by SEM. This was done toinvestigate the morphology of the produced catalysts. In FIG. 6conventional and mesoporous TS-1 are compared to the desilicatedcounterparts. Conventional TS-1, FIG. 6a , shows clearly defined cubiccoffin shaped crystals with sizes of 0.2-0.4 μm. With crystals in thissize range, the diffusion limitations have been decreased to a minimum,without introducing mesopores. Desilicated TS-1 are shown in FIG. 6b .It shows an agglomerate of smaller crystals, with no clear consistentstructure or size. Compared to the conventional TS-1, the mesoporoussample in FIG. 6c is much bigger, with crystal sizes in the range of1.5-2.5 μm. While the surface for the conventional TS-1 is very smooth,the mesoporous sample exhibits a more “sponge”-like shape. Thedesilicated mesoporous TS-1, FIG. 6d , shows some of the samecharacteristics as the other desilicated sample. These similarities arethe agglomeration of smaller crystals, and no clear structure or size.The shape of the original mesoporous sample can however faintly be seen.

SEM images of the propene treated nickel and iron samples are shown inFIG. 7. The reason for the higher carbon uptake on the nickel samplesare clear here. Several carbon nanofibers are present on the nickelsample, and absent on the iron sample. This was expected as, nickel isknown for creating carbon whiskers at high temperatures in the presenceof hydrocarbons [42]. To examine whether the iron nanoparticles wereunchanged within the zeolite and encapsulated in carbon, TEM analysiswill have to be done. TEM analysis will also be interesting, as todetermine the size of the produced nanoparticles, both before and aftersynthesis.

FIG. 8 is a picture of the titanium containing zeolites prepared throughthe coking of nickel nanoparticles. The sample presented in FIG. 8, hasa C/SiO₂ ratio=0.75, and showed mesoporosity visible with SEM. Inaddition, all silica was also converted to zeolites.

Characterization of Catalysts—Energy Dispersive X-ray Spectroscopy

EDS was used to qualitatively determine the elements present in thesamples. All TS-1 catalysts synthesised showed the presence of titanium,silicon and oxygen. Furthermore the samples prepared through coking ofnickel nanoparticles, also showed presence of nickel. To get an exactvalue of the nickel present in the sample, a method consisting ofdissolution of the zeolite, followed by Inductively Coupled Plasma (ICP)could be applied.

Characterization of Catalysts—Nitrogen Phvsisorption

The textural properties of the synthesized materials were determined byadsorption-desorption analysis with nitrogen. The observed SBET,external surface areas, Sext, micropore and total pore volumes arecollated in Table 2. The BET value is less for cdTS-1 and cTS-1.Logically the samples exhibit increasing external surface area after theintroduction of mesoporosity. cTS-1 has the highest external surface,dTS-1 somewhat lower, and cdTS-1 curiously has a value which correspondswith the average of cTS-1 and dTS-1. The same is the case for themicropore volumes. FIG. 9 shows the isotherms of the samples. Accordingto the IUPAC classification of physisorption isotherms, the conventionalTS-1 has a type I isotherm with a sharp transition in the adsorptionbranch at P/P₀<0.1 and almost no adsorption at intermediate relativepressures. This is typical for purely microporous materials such aszeolites.

At P/P₀>0.9 further nitrogen uptake takes place due to the interparticleadsorption within the voids between the small zeolitic particles asobserved in the SEM analysis for conventional TS-1. cTS-1, dTS-1 andcdTS-1 exhibit the type IV isotherms with clearly visible hysteresisloops, which are typical for mesoporous materials. The mesoporoussamples created by carbon templating of TS-1, present hysteresis loopsat P/P₀>0.86 and can be attributed to the interparticle adsorptionwithin the voids formed between the zeolitic particles, or more likelydue to creation of some very large pores, which would be in line withobservation of large, SEM visible porosity in the cTS-1 sample. dTS-1(and cdTS-1 to a smaller extent) show smaller hysteresis loop closing atP/P₀>0.42 with less generation of mesopores compared to micropores.These could be from the voids existing between the nanocrystallites dueto the desilication, but they are more likely to originate from theso-called TSE-effect [81, 82] where capillary evaporation duringdesorption occurs via a hemispherical meniscus, separating the vapourand the capillary condensed phase [83].

TABLE 2 Nitrogen physisorption data for the investigated catalysts.S_(BET) S_(ext) V_(Micro) V_(p) Sample m²/g m²/g cm³/g cm³/g TS-1 390166 0.0915 0.224 dTS-1 346 225 0.0498 0.478 cTS-1 367 136 0.0981 0.448cdTS-1 353 182 0.0731 0.622

Barrett-Joyner-Halenda (BJH) analysis of desorption branch furtherindicate secondary a mesopore distributions in the TS-1 derivedcatalysts. This mesoporosity is created at the expense of the decreaseof micropore volume as seen in Table 2, especially for cTS-1 and cdTS-1,and an increase of the external surface compared to the value of TS-1 asmentioned above. For cTS-1 calcination of carbon template createmesoporous of around 19 nm and around 59 nm for cdTS-1. The dTS-1catalyst exhibits mesopores around 60 nm but in lesser amount as shownin FIG. 10.

The zeolite prepared trough coking of nickel nanoparticles,Ni-0.74-TS-1, was also characterised with nitrogen physisorption. FIG.11 shows the adsorption/desorption isotherms of the zeolite. The sampleshows a clear type IV isotherm, with hysteresis loops at P/P₀>0.80, mostlikely to originate from mesopores. The hysteresis loop aroundP/P₀>0.18, has still yet to be assigned to a structural property. TheBJH pore size distribution, FIG. 12, confirms the presence of mesoporesof the same size (19 nm) as the carbon templated TS-1, but in a muchsmaller magnitude. In addition, the size of the micropores are slightlysmaller than the conventional TS-1, and similar to the TS-1 zeolitesprepared by carbon templated. The mesoporosity of the Ni-0.74-TS-1 isalso confirmed by the Vp result presented in Table 3. With a value of0.323 cm³/g, this is nearly 1.5 times greater than the conventional TS-1synthesised. In addition, the external surface area of Ni-0.74-TS-1, isalso larger, at 189 m²/g compared to 166m²/g of the conventional TS-1.

TABLE 3 Nitrogen physisorption data for the synthesised Ni-0.74-TS-1.S_(BET) S_(ext) V_(Micro) V_(p) Sample m²/g m²/g cm³/g cm³/gNi-0.74-TS-1 400 189 0.0854 0.323

Characterization of Catalysts—Diffuse Reflectance UV-Vis Spectroscopy

FIG. 13 shows the results of the DR-UV-Vis spectroscopy. TS-1 shows amaximum at 47600 cm⁻¹ (210 nm), which is characteristic from the chargetransfer of oxygen 2p electron to the empty 3d orbit of framework Tispecies in tetrahedral coordination. This band is known as a fingerprintof tetrahedrally coordinated Ti(OSi)₄ species in titanium silicateframeworks. The slightly shift to higher wavelengths. at ca. 45500 cm⁻¹(220 nm) for the desilicated samples suggests the simultaneous presenceof tetrahedral tripodal Ti(OSi)₃OH and tetrapodal Ti(OSi)₄. This mightbe a due to an increased surface density of Ti⁴⁺, due to thedesilication process. This effect is only apparent in the desilicatedsamples, cdTS-1 and dTS-1.

Furthermore, dTS-1 shows a broad band at 38400-33300 cm⁻¹ (260-300 nm)that can be attributed to the partially polymerized hexacoordinatednon-framework Ti species, which contain Ti—O—Ti bonds [84, 85]. Thisstrongly suggest a densitification of titania species, most likely onthe outside of the zeolite framework. In addition, cTS-1 and cdTS-1 alsoshows a broad band between 31250-29400 cm⁻¹ (320-340 nm), which istypical for larger extraframework TiO₂ particles with a structuresimilar to anatase. This suggest that the carbon-templating techniquemight also interfere with the active titania sites to some degree,perhaps by provoking some agglomeration of titania species near themesopore channels, which could be thought to occur from the creation ofhotspots during the carbon burnout. Overall, the titania species appearless harmed by the carbon-template method compared to the desilicationmethod.

For an easier comparison, TS-1 is also shown in FIG. 14. Ni-0.74-TS-1shows a maximum at around 47600 cm⁻¹ (210 nm), just as conventionalTS-1. In addition it shows the same tendency to absorb in the broad bandbetween 31250-29400 cm⁻¹ (320-340 nm), just like the other carbontemplated zeolites.

Synthesis—Methane Based Method

As an alternative to the propene based synthesis shown and discussedabove, the zeolites prepared by the new synthesis method disclosed inthis application may be prepared by the following method using methaneto form the carbon template coated zeolite, zeolite-like or zeotypeprecursor composition: First, 5 grams of silica are impregnated toincipient wetness with a nickel nitrate solution. The resultingmaterials typically contained around 2 wt % of Ni metal. This is allowedto stand overnight. The solid is then placed in a tube oven and heatedto 600° C. in argon flow, with a subsequent change of gas to 10%hydrogen in nitrogen for 4 hours. The temperature is reduced to 550° C.under argon. As an alternative to reducing the temperature to 550° C.under argon atmosphere, it may be increased to 700° C. still under argonatmosphere.

Methane gas is then applied for between 10 minutes and up to 12 hours.Preferably, methane is added for between 2-8 hours, or approximately 6hours if the temperature is kept at 550° C. If the temperature is keptat 700° C., methane is normally applied for a shorter time of 10 minutesto 4 hours, or for 2-3 hours. Afterwards, the oven is cooled to roomtemperature with a flow of Ar.

In a 20 ml Teflon beaker 0.5 g of the materials from above areimpregnated with 2.95 ml of 20% TPAOH (tetrapropylammonium hydroxide)solution. 10-20 ml of water is introduced to a 300 ml stainless steelautoclave. The Teflon beaker is placed in the water in the bottom of theautoclave. The closed autoclave is heated to 180° C. for 72 hours.Afterwards, the solid is washed with demineralized water. Thezeolite/carbon composition is then heated to 550° C. for 24 hours toremove the carbon.

The TEM image of the above zeolite produced using methane, where thematerial is heated to 550° C. under argon before methane gas is added,is displayed in FIG. 15.

The SEM image of the above zeolite produced using methane, where thematerial is heated to 700° C. under argon before methane gas is added,is displayed in FIG. 16.

In FIG. 17a and FIG. 17b , the XRPD pattern of MFI zeolite synthesizedusing methane is displayed, where FIG. 17a represents a synthesismethod, where the material is heated to 550° C. under argon beforemethane gas is added and FIG. 17b represents a synthesis method, wherethe material is heated to 700° C. under argon before methane gas isadded.

As can be seen when comparing FIG. 5 with FIG. 17a and FIG. 17b , verylittle variation is observed in the XRPD pattern depending on whichgaseous hydrocarbon that is used in the synthesis and at whichtemperature the sample is heated.

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1. A method for producing zeolite, zeolite-like or zeotype encapsulatedmetal nanoparticles, comprising: 1) Adding one or more metal precursorsto a silica or alumina source; 2) Reducing the one or more metalprecursors to form metal nanoparticles on the surface of the silica oralumina source; 3) Passing a gaseous hydrocarbon, alkyl alcohol or alkylether over the silica or alumina supported metal nanoparticles to form acarbon template coated zeolite, zeolite-like or zeotype precursorcomposition; 4a) Adding a structure directing agent to the carbontemplate coated zeolite, zeolite-like or zeotype precursor compositionthereby creating a zeolite, zeolite-like or zeotype gel composition; 4b)Crystallising the zeolite, zeolite-like or zeotype gel composition bysubjecting said composition to a hydrothermal treatment; and 5) Removingthe carbon template and structure directing agent and isolating theresulting zeolite, zeolite-like or zeotype encapsulated metalnanoparticles; wherein the carbon template coated zeolite, zeolite-likeor zeotype precursor composition of step 3 is used directly in step 4awithout removing the silica or alumina source. 2-16. (canceled)
 17. Themethod for producing zeolite, zeolite-like or zeotype encapsulated metalnanoparticles according to claim 1, wherein the one or more metal(s) isselected from the group consisting of group 4 elements, group 6elements, group 7 elements, group 8 elements, group 9 elements, group 10elements, group 11 elements and group 12 elements or mixtures thereof.18. The method for producing zeolite, zeolite-like or zeotypeencapsulated metal nanoparticles according to claim 1, wherein the oneor more metal(s) is selected from the group consisting of titanium,osmium, iridium, platinum, ruthenium, palladium, rhodium, rhenium,copper, nickel, iron, cobalt, silver, gold, cadmium, and molybdenium ormixtures thereof.
 19. The method for producing zeolite, zeolite-like orzeotype encapsulated metal nanoparticles according to claim 1, whereinthe hydrocarbon is selected from the group consisting of aliphatichydrocarbons having 1 to 8 carbon atoms, having 1 to 3 carbon atoms,alkenes having 2 to 6 carbon atoms, aromatic hydrocarbons having 6 to 10carbon atoms and cyclic hydrocarbons having 3 to 8 carbon atoms.
 20. Themethod for producing zeolite, zeolite-like or zeotype encapsulated metalnanoparticles according to claim 1, wherein the one or more metalprecursor is loaded to the silica or alumina in an amount of from 0.5 to20 wt %, from 0.5 to 5 wt %, from 0.5 to 2 wt %, or 1 wt % duringstep
 1. 21. The method for producing zeolite, zeolite-like or zeotypeencapsulated metal nanoparticles according to claim 1, comprising addingan Al, Sn Ti, Zr or Ge source during step 4a.
 22. The method forproducing zeolite, zeolite-like or zeotype particles according to claim1, wherein the hydrothermal treatment comprises heating the zeolite,zeolite-like or zeotype gel composition to a temperature between 70 and300° C., or 180° C., under an autogeneous pressure in an autoclave oropen flask for 24 hours or more.
 23. A zeolite, zeolite-like or zeotypeencapsulated metal nanoparticles manufactured by the method according toclaim
 1. 24. A zeolite, zeolite-like or zeotype encapsulated metalnanoparticles according to claim 23, wherein said metal nanoparticlesare located predominantly in the secondary porosity of the zeolitestructure, or more than 70%, more than 80%, more than 90% or more than95% of the total amount of the encapsulated metal nanoparticles.
 25. Thezeolite zeolite-like or zeotype encapsulated metal nanoparticlesaccording to claim 23, wherein the particle is a hierarchical mesoporouszeolite, zeolite-like or zeotype particle.
 26. The zeolite, zeolite-likeor zeotype encapsulated metal nanoparticles according to claim 23,wherein the amount of metal nanoparticles are in the range from 0.1 to25 wt %, 0.5 to 20 wt %, 0.5 to 10 wt %, 0.5 to 5%, 1.0 to 5 wt %, 1 to2 wt %, or 1 wt %.
 27. The zeolite, zeolite-like or zeotype encapsulatedmetal nanoparticles according to claim 23, wherein the one or moremetal(s) is selected from the group consisting of group 4 elements,group 6 elements, group 7 elements, group 8 elements, group 9 elements,group 10 elements, group 11 elements and group 12 elements or mixturesthereof.
 28. The zeolite, zeolite-like or zeotype encapsulated metalnanoparticles according to claim 23, wherein the one or more metal(s) isselected from the group consisting of titanium, osmium, iridium,platinum, ruthenium, palladium, rhodium, rhenium, copper, nickel, iron,cobalt, silver, gold, cadmium, and molybdenum or mixtures thereof. 29.The zeolite, zeolite-like or zeotype encapsulated metal nanoparticlesaccording to claim 23, comprising an Al, Sn, Ti, Zr or Ge source in theframework of the crystal structure.
 30. A method of using the zeolite,zeolite-like or zeotype encapsulated metal nanoparticles according toclaim 23 in shape-selective catalysis comprising: Providing the zeolite,zeolite-like or zeotype encapsulated metal nanoparticles according toclaim 23; and Conducting shape-selective catalysis using saidnanoparticles.